JBC, Vol. 250, Issue 17, 6735-6746, Sep, 1975
Primary amino acid sequence of follicle-stimulating hormone from human pituitary glands. I. alpha subunit
P. Rathnam and B. B. Saxena
Follicle-stimulating hormone of a high state of physicochemical and
biological purity was isolated from acetone-preserved human pituitary
glands. The follicle-stimulating hormone was dissociated into alpha and
beta subunits by treatment with 8 M urea and the subunits were separated by
ion exchange chromatography on DEAE-Sephadex A-25. The subunits were freed
of undissociated or reassociated follicle-stimulating hormone by gel
filtration on Sephadex G-100. For the establishment of the primary amino
acid sequence, the alpha subunit was reduced and either
carboxyamidomethylated or S-aminoethylated prior to a thermolytic or a
tryptic digestion. Each digest was gel filtered on a column of Sephadex
G-50 to separate the glycopeptides from the peptides. The glycopeptides and
the peptides were purified further by sequential gel filtration on Sephadex
G-25, G-15, and Bio-Gel-P-2 and were isolated by high voltage
electrophoresis at pH 6, 3.5, and 2. The purity of the isolated peptides
was ascertained further by amino acid analysis. The amino acid sequences of
the peptides were determined by Edman degradation followed by subtractive
amino acid analysis. COOH-terminal sequences were established by digestion
with carboxypeptidases A and B. The primary amino acid sequence of human
follicle-stimulating hormone-alpha is identical to that of human chorionic
gonadotropin-alpha and differs from that of human luteinizing hormone-alpha
in having the tripeptide Ala-Pro-Asx- at the NH2-terminal end.